feat: 🎸 implement initial version of appendFile() method

src/fsa-to-node/FsaNodeFs.ts

@@ -7,9 +7,11 @@ import {
   getRmOptsAndCb,
   getRmdirOptions,
   optsAndCbGenerator,
+  getAppendFileOptsAndCb,
 } from '../node/options';
 import {
   createError,
+  dataToBuffer,
   flagsToNumber,
   genRndStr6,
   isFd,
@@ -96,6 +98,14 @@ export class FsaNodeFs implements FsCallbackApi {
     return await this.getFile(folder, name, funcName);
   }
 
+  private async getFileByIdOrCreate(id: misc.TFileId, funcName?: string): Promise<fsa.IFileSystemFileHandle> {
+    if (typeof id === 'number') return (await this.getFileByFd(id, funcName)).file;
+    const filename = pathToFilename(id);
+    const [folder, name] = pathToLocation(filename);
+    const dir = await this.getDir(folder, false, funcName);
+    return await dir.getFileHandle(name, { create: true });
+  }
+
   public readonly open: FsCallbackApi['open'] = (
     path: misc.PathLike,
     flags: misc.TFlags,
@@ -280,16 +290,19 @@ export class FsaNodeFs implements FsCallbackApi {
     throw new Error('Not implemented');
   }
 
-  appendFile(id: misc.TFileId, data: misc.TData, callback: misc.TCallback<void>);
-  appendFile(
-    id: misc.TFileId,
-    data: misc.TData,
-    options: opts.IAppendFileOptions | string,
-    callback: misc.TCallback<void>,
-  );
-  appendFile(id: misc.TFileId, data: misc.TData, a, b?) {
-    throw new Error('Not implemented');
-  }
+  public readonly appendFile: FsCallbackApi['appendFile'] = (id: misc.TFileId, data: misc.TData, a, b?) => {
+    const [opts, callback] = getAppendFileOptsAndCb(a, b);
+    const buffer = dataToBuffer(data, opts.encoding);
+    this.getFileByIdOrCreate(id, 'appendFile')
+      .then(file => (async () => {
+        const blob = await file.getFile();
+        const writable = await file.createWritable({ keepExistingData: true });
+        await writable.seek(blob.size);
+        await writable.write(buffer);
+        await writable.close();
+      })())
+      .then(() => callback(null), error => callback(error));
+  };
 
   public readonly readdir: FsCallbackApi['readdir'] = (path: misc.PathLike, a?, b?) => {
     const [options, callback] = getReaddirOptsAndCb(a, b);

src/fsa-to-node/__tests__/FsaNodeFs.test.ts

@@ -286,3 +286,24 @@ describe('.readdir()', () => {
     expect(list.find(item => item.name === 'f.html')?.isDirectory()).toBe(false);
   });
 });
+
+describe('.appendFile()', () => {
+  test('can create a file', async () => {
+    const { fs, mfs } = setup({});
+    await fs.promises.appendFile('/test.txt', 'a');
+    expect(mfs.readFileSync('/mountpoint/test.txt', 'utf8')).toBe('a');
+  });
+
+  test('can append to a file', async () => {
+    const { fs, mfs } = setup({});
+    await fs.promises.appendFile('/test.txt', 'a');
+    await fs.promises.appendFile('/test.txt', 'b');
+    expect(mfs.readFileSync('/mountpoint/test.txt', 'utf8')).toBe('ab');
+  });
+
+  test('can append to a file - 2', async () => {
+    const { fs, mfs } = setup({ file: '123'});
+    await fs.promises.appendFile('file', 'x');
+    expect(mfs.readFileSync('/mountpoint/file', 'utf8')).toBe('123x');
+  });
+});

src/node/options.ts

@@ -1,8 +1,9 @@
 import type * as opts from './types/options';
-import { MODE } from './constants';
+import { FLAGS, MODE } from './constants';
 import { assertEncoding } from '../encoding';
 import * as misc from './types/misc';
 import { validateCallback } from './util';
+import {IAppendFileOptions} from '../volume';
 
 const mkdirDefaults: opts.IMkdirOptions = {
   mode: MODE.DIR,
@@ -78,3 +79,11 @@ export const getReaddirOptions = optsGenerator<opts.IReaddirOptions>(readdirDefa
 export const getReaddirOptsAndCb = optsAndCbGenerator<opts.IReaddirOptions, misc.TDataOut[] | misc.IDirent[]>(
   getReaddirOptions,
 );
+
+const appendFileDefaults: opts.IAppendFileOptions = {
+  encoding: 'utf8',
+  mode: MODE.DEFAULT,
+  flag: FLAGS[FLAGS.a],
+};
+export const getAppendFileOpts = optsGenerator<IAppendFileOptions>(appendFileDefaults);
+export const getAppendFileOptsAndCb = optsAndCbGenerator<IAppendFileOptions, void>(getAppendFileOpts);

src/node/util.ts

@@ -2,6 +2,8 @@ import { ERRSTR, FLAGS } from './constants';
 import * as errors from '../internal/errors';
 import type { FsCallbackApi } from './types';
 import type * as misc from './types/misc';
+import {ENCODING_UTF8} from '../encoding';
+import {bufferFrom} from '../internal/buffer';
 
 export const isWin = process.platform === 'win32';
 
@@ -168,3 +170,9 @@ export function isFd(path): boolean {
 export function validateFd(fd) {
   if (!isFd(fd)) throw TypeError(ERRSTR.FD);
 }
+
+export function dataToBuffer(data: misc.TData, encoding: string = ENCODING_UTF8): Buffer {
+  if (Buffer.isBuffer(data)) return data;
+  else if (data instanceof Uint8Array) return bufferFrom(data);
+  else return bufferFrom(String(data), encoding);
+}

src/volume.ts

@@ -27,6 +27,8 @@ import {
   optsAndCbGenerator,
   optsDefaults,
   optsGenerator,
+  getAppendFileOptsAndCb,
+  getAppendFileOpts,
 } from './node/options';
 import {
   validateCallback,
@@ -39,6 +41,7 @@ import {
   validateFd,
   isFd,
   isWin,
+  dataToBuffer,
 } from './node/util';
 import type { PathLike, symlink } from 'fs';
 
@@ -121,13 +124,6 @@ const getWriteFileOptions = optsGenerator<IWriteFileOptions>(writeFileDefaults);
 
 // Options for `fs.appendFile` and `fs.appendFileSync`
 export interface IAppendFileOptions extends opts.IFileOptions {}
-const appendFileDefaults: IAppendFileOptions = {
-  encoding: 'utf8',
-  mode: MODE.DEFAULT,
-  flag: FLAGS[FLAGS.a],
-};
-const getAppendFileOpts = optsGenerator<IAppendFileOptions>(appendFileDefaults);
-const getAppendFileOptsAndCb = optsAndCbGenerator<IAppendFileOptions, void>(getAppendFileOpts);
 
 // Options for `fs.realpath` and `fs.realpathSync`
 export interface IRealpathOptions {
@@ -229,12 +225,6 @@ export function dataToStr(data: TData, encoding: string = ENCODING_UTF8): string
   else return String(data);
 }
 
-export function dataToBuffer(data: TData, encoding: string = ENCODING_UTF8): Buffer {
-  if (Buffer.isBuffer(data)) return data;
-  else if (data instanceof Uint8Array) return bufferFrom(data);
-  else return bufferFrom(String(data), encoding);
-}
-
 export function bufferToEncoding(buffer: Buffer, encoding?: TEncodingExtended): TDataOut {
   if (!encoding || encoding === 'buffer') return buffer;
   else return buffer.toString(encoding);
@@ -1475,7 +1465,7 @@ export class Volume {
     this.wrapAsync(this.accessBase, [filename, mode], callback);
   }
 
-  appendFileSync(id: TFileId, data: TData, options: IAppendFileOptions | string = appendFileDefaults) {
+  appendFileSync(id: TFileId, data: TData, options?: IAppendFileOptions | string) {
     const opts = getAppendFileOpts(options);
 
     // force append behavior when using a supplied file descriptor